Improvement in toughness and flame retardancy of bismaleimide/diallyl bisphenol A resin with a eugenol allyl ether-grafted polysiloxane

Despite bismaleimide/2,2′-diallyl bisphenol A (BD) resin has been successfully used as a high-performance thermosetting resin, it is needed to further improve its toughness and flame retardancy to meet the requirements of application in harsh environments. In this study, we synthesized a eugenol allyl ether grafted polysiloxane (PMES-Allyl), and used it as an allyl compound to modify BD resin to obtain a new BDPA resin. The eugenol structure helped to improve the compatibility of the polysiloxane with the BD resin. When the addition amount of PMES-Allyl was 15 wt%, PMES-Allyl could be well dispersed in the resin matrix, leading to a significant increase of crosslinking density. As a result, the cured BDPA15% resin had better toughness than the cured BD resin, with the impact strength and flexural strength reaching 17.9 kJ/m2 and 177.1 MPa, respectively. Compared to the cured BD resin, the cured BDPA15% resin showed a comparable glass transition temperature and thermal stability, while an improved char yield. The active role of PMES-Allyl in helping the resin form an expanded, dense and stable char during heating, further made the cured BDPA15% resin exhibit an excellent flame retardancy. Compared with the cured BD resin, the cured BDPA15% resin showed a decrease of peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) by 58.6 %, 33.1 %, and 41.9 %, respectively, as well as a reduced release amount of the gasified pyrolysis products. This study provides a new insight and method for improving the properties of BD resin.